﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!!!");

            double dd = 3.14;
            double sum;
            Console.WriteLine("请输入圆的半径");
            double d = double.Parse(Console.ReadLine());
            sum = d * d * (3.14);
            Console.WriteLine("圆的面积是：" +sum);
            Console.ReadKey();
        }
    }
}
